Method of preparing a dry size



PatentedNov. 26, 1946 UNITED" STATES. PATENT orncs METHOD OF EPAR G a pay size James -K. Farrell, Wilmington, :DeL, assignor to Hercules Powder Company, Wilmington, Del a corporation of Delaware N Drawing. Application May 14, 1-945, Serial No. 593,759

ployed involves introducing the rosin and aqueous solution ofalkaliintoa closedreaction-cham- 'ber, heating the-saponifying materials to an elevated temperature and under superatmospheric pressure, and :then discharging the saponification mixture at the elevated:temperatureand pressure into a zone in which a drying atmosphere is maintained at substantially atmospheric pressure, thereby substantially completelydesiccating the saponification mixture to provide a dry, finely-dividedsaponifiedrosin size. It has been proposed to carry-out this general type of method either in an intermittent fashion or in a continuous manner.

Saponified rosin dry size heretofore produced by such methods has been undesirably light and flufiy. Generally speaking, it has had an apparent density in bulk in the order of about 4 to about 12 pounds per cubic foot. Because of the large volume occupied by a given weight of such size, vits packaging, handling, and the like, have been inconvenient and unduly expensive.

The apparent densityin ,bulk of such dry size may be increasedduring packaging to about 15 pounds per cubic foot by forcing,.or ramming, the

particles into the bags or othercontainers so as to compact-theparticles into smaller ones which occupy less space and therefore have a higher apparent density in bulk. Theapparent density of the dry size also may be increased by compacting the sizep'articles and subsequently comminuting the compacted particles andseparating out the particleshaving the desired size to obtain a product havinga higher apparent density in bulk.

, Such methods of increasing the apparent density of saponified rosin dry size have-certain disadvantages whichrender them not.entirely(satisfactory. Forcing of'the sizeparticles-into bags or. othercontainers does not lead toasgreat an increase ,in density as is desirable. Because of the high pressures that must be applied adequately to reduce the volumeof the si .an excessive number of bags are broken in thaprocess, lnvolvingadirect lossof money as well as of time en ima er al l he shatt in o the part cles also leads to the formation of excessive quantities of dust, such dust being both inconvenient and disagreeable during handling and use of the size.

Compacting and subsequently comminuting the size and .separating out the desired particles in.-

volve additional steps in the production process that require additional equipment otherwise not needed. Additional time is required in the process, and the cost of the treatment tends to offset any savings that otherwise {would be accom- The present invention provides a method whereby a saponified rosin dry size in finely-divi e form n ha i an a pa n d it i bulk of from about 20 to about pounds per cubic foot may be produced directly by a spraydrying type of process without the necessity of subsequent treatments heretofore employed. The invention thus serves to overcome the disadyahtageoiis featiires of methods heretofore available for thelproduction of saponified rosin dry size and also serves to provide an improved size product ,free of certain undesirable characteristics'of the low apparentdensity products prev-iously available.

Generally speaking, the present invention inv'olves a methodof preparing saponified rosin dry sizein the ,form of discrete, free-flowing particles readily soluble in water and having a high apparent. density in bulk, which comprises saponifyin g rosin with an aqueous solutionof an alkali metal alkali and then discharging an aqueous mixture comprising the saponifled rosin and containing not lessthan 22and upto about 30% by weight of water, based on the total weight of saponified rosin and Watenat an,elevatedtemperature and pressure, into a drying atmosphere maintained at substantially atmospheric pressure and at a temperature of from about 240 to about 325 F., thereby obtaining thesaponified rosin dry size in a ,finelyrdivided form containing not over about 8% moisture and having an apparent density in bulk of from about 20 toabout 35 pounds per cubic foot. ;The '.i nvention.also includes the particular conditions and methods of operation which, i n conjunction with the described steps,

lead to the formation of theimproved product.

The product obtainedin accordance .With the present invention comprises discrete, readily wateresoluble, noncompactedparticles of areaction productof an alkali metal alkali and rosin, being ubs an ll esic ate a dhe ne an app nt bulk-density-of -f;romabout-2 0 to about-35 pounds per-cubicfoot. The productis substantially non dusty,-con-t;aining-lessthan;5%, of particles capa- 3 ble of passing through a No. 200 mesh sieve, but containing about 25% of particles capable of passing through a No. 100 mesh sieve. The product is substantially completely desiccated, containing less than about 8% and preferably less than about 3.5% moisture.

The improved product, because of its high apparent density in bulk, may be packaged in smaller containers than heretofore necessary, thereby providing more efficient utilization of containers as well as of storage and shipping space. The nondustiness of the size product renders its handling and use more convenient and agreeable. The method of the present invention provides this improved product directly by a spray-drying process and without subsequent treatments. The process of the invention therefore provides important advantages from the standpoint of production and greatly simplifies the production of saponified rosin dry size having high apparent density in bulk.

Having set forth the broader aspects of the invention, the following examples will serve to illustrate certain specific embodiments thereof. In the examples, all quantities of materials are given in parts by weight unless otherwise specified.

Eztample 1 'Two thousand parts of gum rosin having an acid number of 165 was melted and introduced into an autoclave of the type customarily used for saponification of rosin. A 39% solution of sodium hydroxide in water, containing 240 parts of alkali, was injected into the molten rosin. The mixture was heated to a temperature of about 360 F. and under a pressure of about 135 to about 140 pounds per square inch for a period of about 10 minutes. Then 284 parts of water was injected into the saponification mixture while maintaining the temperature at about 360 F. After completion of the saponification reaction, the contents of the autoclave contained 26.5% water, based on the total weight of saponified rosin plus water. The mixture then was discharged at the stated temperature and pressure countercurrent to a drying atmosphere circulating through a blow chamber and heated to a temperature of about 260 F. and under substantially atmospheric pressure. The saponification mixture thereby was dispersed into finely-divided particles and rapidly converted to a substantially completely desiccated state. The size product was collected as a finely-divided dry powder. It contained approximately 3.4% moisture. It had an apparent density in bulk of 25.2 pounds per cubic foot and contained 0.13% free alkali.

Example 2 Gum rosin was partially saponified with an aqueous solution of sodium carbonate in water to provide a paste size containing about 15.5% water and about 26.8% free rosin on a dry basis. One thousand parts of the paste size was introduced into an autoclave, and 27.4 parts sodium 4 ture to a fine dry powder. The dry size thus obtained was found to have an apparent density in bulk of about 26 pounds per cubic foot and to contain about 3% moisture by weight.

To illustrate the critical efiect of the amount of water contained in the saponification mixture upon the apparent density of the size product in bulk, a second lot of dry size was prepared as above, but adding only sufficient water to the paste size to provide a saponification mixture containing 17.5% water. A dry size product prepared from this mixture under otherwise similar conditions had an apparent density in bulk of only about 11.5 pounds per cubic foot.

Example 3 To illustrate further certain aspects of the present invention and the desirable results attained thereby, three saponified rosin size compositions were prepared by saponifying a mixture of wood rosin and gum rosin containing gum rosin and 15% wood rosin, by treatment with concentrated sodium hydroxide solution in an autoclave at elevated temperature and under superatmospheric pressure. The saponification mixtures at the completion of the saponification reaction were found to have the contents of water shown in the table presented below. Each of the aqueous saponification mixtures then was discharged at a temperature of about 365 F. and under a pressure of about pounds per square inch countercurrent to a circulating drying atmosphere maintained at substantially atmospheric pressure and heated to a temperature of about 260 F. so as to substantially completely desiccate the mixture. A comparison of the apparent densities of the three products thus obtained is shown in the table presented below. Each of the products contained less than 5 moisture.

Water content of Apparent density saponification in bulk of product, mixture lbs./cu. it.

Percent A shown by the examples, the first step in the present process involves saponifying a rosin with a concentrated aqueous solution of an alkali metal alkali to provide an aqueous saponification product of rosin and alkali. Sodium hydroxide is the preferred alkali, although other alkali metal alkalies may be employed. Thus, a portion of the caustic alkali may be replaced by sodium carbonate, if desired, as by first preparing a soda-cooked paste size using an amount of sodium carbonate up to about 80% of the theoretical equivalent of the rosin. In such a case, the saponification of the rosin is completed with the concentrated caustic alkali in an autoclave, as in Example 2, and the remainder'of the process is carried out as herein described. Because ofv the difference in cost between caustic soda and sodium carbonate, it often is advantageous to proceed in this manner. The total amount of alkali employed is such that a substantially neutral size product is obtained. Thus, there is employed an amount of alkali adapted to provide a size product containing from not more than about 8.0% free rosin to not more than about 0.5% free alkali.

As the rosin, there may be employed either 75 gum or wood rosin in any of the several color steam.

grades, or mixtures of the-same. Alternatively, the acids occurring in such rosins, such as abietic acid, pimario acid, sapinic .acid, etc., may be employed. I The present invention also is suited to th preparation of improved size products from modified rosins, such as heat-treated rosin, dehydrogenated rosin, hydrogenated rosin, partially polymerized rosin, and other modified rosins, such as are known to the art. The addition :of various modifying agents, such as waxes, parafvfin oils, antioxidants, and the like, to the .size, either before orafter the drying step, also is contemplated. The addition to the saponification mixture-of from aboutto about 50% of .a paraffin wax, based on the dry weight of saponified rosin, serves to provide a dry size composition having advantages in certain paper .sizing processes.

In accordance with the present invention, the water content of the final aqueous saponification mixture is of critical importance to obtaining the benefits of the invention. The water content should be not less than 22% by weight and may be up to about 30% by weight of the mixture. Preferably, the water con-tent is maintained between about 23 and about 28% of the mixture. "It has been found that the apparent density of the product is closely related to this condition. :As shown in Examples 2 and 3, decreasing the water content of the saponification mixture to a value below 22% leads toa low density product that differs Jmarkedly fromthe herein-disclosed improved dry size. These examples illustrate the importance .of this particular factor in providing the product of high bulk density.

The desired water content in the saponification mixture may be obtained bysaponifying the rosin with, for example, .a highly concentrated solution of caustic alkali and subsequently adding to the mixture sumcient water to provide the desired content of water. Alternatively, the concentration of the caustic alkali may be adjusted so as to provide directly the necessary amount of water. In determining beforehand the amounts of the various materials to be employed to obtaina desired water content, the amount of water formed by the reaction of the saponifying materials .preferably is taken into account, the

necessary stoichiometric calculations based on the saponification number of the rosin and the quantity of alkali added being readily apparent to those skilled in the art. I

At-any time before or after the saponification reaction, but prior to the drying step, the mixture is heated to a temperature of from about 340 to about 380 151., preferably 360 to about 375 R, and under superatmospheric pressure. The pressure may be the equilibrium pressure developed at'the particular temperature employed,

and thus be from about 110 to about 170 pounds per square inch, or, if desired, an external pressure of, say,up to about 200 pounds per inch may be applied to the contents of the autoclave by means of, for instance, compressed air or dry The application of such external pressure is advantageous in that it facilitates carry- .ing'out theprocess under constant conditions and hence facilitates successful practice of the invention. 3

The saponification mixture at the stated temperature and pressure and containing between not less than 22% water and up to about 30% Water, preferably from about 23 to about 28% water, then is discharged into the drying atmosphere to effect desiccation of the mixture and formation of the final product. The improved results of this invention are closely related to the temperature and humidity conditions of the atmosphere. The atmosphere is maintained .at a temperature of from about 240 to about 325 F., and at substantially atmospheric pressure. The relative humiditycf the heated air after drying the product, referred toa temperature of 200 is :maintained at a value below about 10%. Higher temperatures of the drying atmosphere tend to cause decomposition of the size and a consequent decrease in its quality, whereas at lower temperatures .or higher humidities, the size product tends to be insuniciently desiccated and, therefore, to revert from the finely-divided condition to a more massive state.

Heretofore it has been found possible to employ considerably broader conditions of temperatur and humidity in the drying step. The interdependence of the present conditions of drying with other aspects of the process is asignifican t feature of the present invention.

When discharged into the drying atmosphere, the stream of liquid saponiflcation mixture is broken up into finely-dispersed particles which are rapidly and substantially completely desiccated to form a fine, free-flowing dry powder. The particles have a somewhat porous structure and are readily dispersible in water. The individual particles generally vary in size, as determined by sieve analysis, according to the following order of gradation: 0% retained on a No. 20 mesh sieve; '70 to retained on a No. 80 mesh sieve; 80 to retained on a No. 140 mesh sieve; and more than retained on a No. 200 mesh sieve. As indicated by the low proportion oi particles passing the finest sieve, the size is substantially nondusty. Viewed in bulk, the size is seen to be characterized by the uniformity in the size of the particles and by the freedom from larger particles which would be less readily dispersible in water. The individual particles are resistant to breakage, as during handling and packaging, and therefore have little tendency to form dust. The size is noncoalescing and freeflowing, and without significant tendency to revert to a more massive state as during storage. The present products containing less than about 3.5% moisture, when placed under a Weight of about .38 pound per square inch at about F. for 24; hours, undergo substantially no change in apparent density. Higher contents of moisture tend to produce a slight settling tendency under these conditions. The present product is readily soluble in water, having a solubility of from about 50 to about 85 seconds in a 3% solution in water. As produced, and without subsequent treatments, such as compaction or compression, the saponified rosin dry size obtained has an apparent'density in bulk of from about 20 to about 35 pounds per cubic foot, and in the preferable cases of from about 25 to about 30 pounds per-cubic foot. The size product,being substantially-completely desiccated, contains less than about 8 and preferably less than about 3.5% moisture.

This present invention thus provides a process for preparing an improved saponiiied rosin-dry size productand theproduct obtained. The improved size product provides advantages of economic savings gained by the decreased cost of packaging as well as savings resulting from more economic handling and storage. Further advantages lie in the fact that the size product is readily soluble in water, free from dust or any substantial tendency to form dust, and noncoalescing. The process of the invention provides the improved product without subsequent treatments, and therefore results in improved efficiency of operation as well as in savings that are obtained as a consequence of the properties of th product.

What we claim and desire to protect by Letters Patent is:

1. A method of preparing a saponified rosin dry size in the form of discrete, free-flowing, readily water-soluble particles and having a high apparent density in bulk, which comprises the step of discharging an aqueous mixture comprising saponified rosin and containing not less than 22 and up to about 30% by weight of water, based on the weight of saponified rosin and water, at a temperature of from about 340 to about 380 F. and under a pressure of from about 110 to about 200 pounds per square inch, into a drying atmosphere maintained at substantially atmospheric pressure and at a temperature of from about 240 to about 325 F., thereby obtaining the saponified rosin dry size in a finelydivided form containing not over about 8% moisture and having an apparent density in bulk of from about 20 to about 35 pounds per cubic foot.

2. A method of preparing a saponified rosin dry size in the form of discrete, free-flowing, readily water-soluble particles and having a high apparent density in bulk, which comprises saponifying a rosin with a substantially chemically equivalent amount of an aqueous solution of an alkali metal alkali to provide a saponification mixture having a water content not less than 22 and up to about 30%, based on the weight of saponified rosin and water, and discharging said saponification mixture-at a temperature of from about 340 to about 380 F. and under a pressure of from about 110 to about 200 pounds per square inch into a drying atmosphere maintained at substantially atmospheric pressure and at a temperature of from about 240 to about 325 F., thereby obtaining substantially desiccated, finely-divided particles of saponified rosin dry size in a form having an apparent density in bulk between about 20 and about 35 pounds per cubic foot.

3. A method of preparing a saponified rosin dry size in the form of discrete, free-flowing, readily water-soluble particles and having a high apparent density in bulk, which comprises saponifying rosin with a substantially chemically equivalent amount of aqueous sodium hydroxide to provide a saponification mixture containing not less than 22 and up to about 30% by weight of water, heating the saponification mixture to a temperature of from about 340 to about 380 F. and under a pressure of from about 110 to about 200 pounds per square inch, and then discharging the saponification mixture at said temperature and pressure countercurrent to a circulating drying atmosphere maintained at substantially atmospheric pressure and at a tern-'- perature of from about 240 to about 325 F.,

thereby substantially completely desiccating the saponification mixture and producing the saponified rosin dry size in finely-divided form containing less than about 8% moisture by weight and having an apparent density in bulk of from about 20 to about 35 pounds per cubic foot.

4. A method of preparing a saponified rosin dry size in the form of discrete, free-flowing, readily water-soluble particles and having a high apparent density in bulk, which comprises saponifying rosin with a substantially chemically equivalent amount of alkali metal alkali in aqueous solution, heating the saponification mixture to a temperature of from about 340 to about 330 F. and under a pressure of from about to about 200 pounds per square inch, providing a water content in the saponification mixture of from at least 22 up to about 30% by Weight of the mixture, and then discharging the saponification mixture having the said water content and at said temperature and pressure into a drying atmosphere maintained at substantially atmospheric pressure and at a temperature of from about 240 to about 325 F., thereby obtaining the saponiiied rosin dry size in a finely-divided, substantially desiccated form having an apparent density in bulk of from about 20 to about 35 pounds per cubic foot.

5. A method of preparing a saponified rosin dry size in the form of discrete, free-flowing, readily water-soluble particles and having a high apparent density in bulk, which comprises saponifying rosin with a substantially chemically equivalent amount of concentrated aqueous sodium hydroxide solution, adjusting the water content of the saponification mixture to not less than 22 and up to about 30% by weight, heating the saponification mixture to a temperature of from about 360 to about 375 F. and under the equilibrium pressure at said temperature, and then discharging the saponification mixture at said temperature and pressure countercurrent to a circulating drying atmosphere maintained at substantially atmospheric pressure and at a temperature of from about 240 to about 325 F., thereby substantially completely desiccating the saponification mixture and producing the saponified rosin dry size in finely-divided form containing less than about 8% moisture by Weight and having an apparent density in bulk of from about 20 to about 35 pounds per cubic foot.

6. A method of preparing a saponified rosin dry size in the form of discrete, free-flowing, readily water-soluble particles and having a high apparent density in bulk, which comprises saponifying rosin with a substantially chemically equivalent amount of sodium hydroxide in the form of a concentrated aqueous solution, heating the saponification mixture to a temperature of from about 360 to 375 F. and under a pressure of from about 110 to about 200 pounds per square inch, providing a water content in the saponification mixture of from at least 22 up to about 30% by weight of the mixture, and then discharging the saponification mixture having the said water content and at said temperature and pressure into a drying atmosphere maintained at substantially atmospheric pressure and at a temperature of from about 240 to about 325 F., thereby obtaining the saponiiied rosin dry size in a finely-divided, substantially desiccated form having an apparent density in bulk of from about 20 to about 35 pounds per cubic foot.

JAMES K. FARRELL. 

